Trigonometry Terms I

Complementary Angles: Learn

A right triangle consists of one angle of 90oand two acute angles.
Each acute angle of a right triangle has the properties of sine, cosine and tangent.

The sine, cosine and tangent of an acute angle of a right triangle are ratios of two of the three sides of the right triangle.

The sine of the angle is the ratio of the length of the side opposite the angle divided by the length of the hypotenuse.

The cosine of the angle is the ratio of the length of the side adjacent to the angle divided by the length of the hypotenuse.

The tangent of the angle is the ratio of the length of the side opposite the angle divided by the length of side adjacent to the angle.

Trigonometry is like a story told from the perspective of one angle in
a right triangle. The diagram below labels the sides of a right triangle
from the perspective of the angle labeled "A". If we switched the story to
the perspective of the other acute angle, the adjacent/opposite sides
would also switch.